The present invention relates to a method for terminating the end of an optical fiber. In particular the present invention relates to a method for forming a low reflectance termination on an end of an optical fiber. The method including the step of tensioning the optical fiber between two spaced apart points thereon. The method further including the step of moving a ball termination torch from a given location in a given direction with respect to the fiber such that a potion of the flame therefrom intercepts the fiber and severs the fiber into two pieces each having a tapered end. The method further includes the steps of retracting at least one of the tapered ends a predetermined distance in a direction away from the other of the tapered ends and continuing to move the torch such that the flame heats the at least one of the tapered ends to cause it to become shortened.
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1. Method for forming a low reflectance termination on an end of an optical fiber comprising
tensioning said optical fiber between two spaced points thereon, moving a ball termination torch from a given location in a given direction with respect to said fiber such that a portion of the flame therefrom intercepts said fiber and severs said fiber into two pieces each having a tapered end, retracting at least one of said tapered ends a predetermined distance in a direction away from the other of said tapered ends, and continuing to move said torch such that said flame heats said at least one of said tapered ends to cause it to become shortened.
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This is a division of application Ser. No. 09/043,758, filed Mar. 25, 1998 U.S. Pat. No. 6,092,394 which is a 371 of PCT/US96/15254 filed Sep. 16, 1996, and claims Benefit to No. 60/004,647 filed Sep. 29, 1995.
The present invention relates to the automated manufacturing of fiber optic couplers.
Overclad fiber optic couplers are a type of fused fiber coupler wherein the coupling region is enclosed within a layer of matrix glass which strengthens and encloses the coupling region. To form an overclad fiber optic coupler, the stripped portions of a plurality of fibers are inserted into the bore of a glass capillary tube to form a coupler preform. The tube bore has enlarged funnel-shaped end portions that facilitate the insertion of optical fibers. The midregion of the coupler preform is heated to collapse the tube onto the fibers; the coupler preform is then stretched until the desired coupling characteristics are obtained. Various types of overclad fiber optic couplers and methods of making such couplers are disclosed in U.S. Pat. Nos. 35,138, 4,902,324, 4,979,972, 5,011,251, 5,251,276 and 5,268,014. The methods disclosed in these patents include many manual operations.
In accordance with conventional practice, the manually operated fiber draw apparatus has been oriented such that the tube is vertically positioned. The fibers have been inserted into the tube either on-line or off-line. The off-line fiber insertion process (U.S. Pat. No. 4,902,324) requires that the fibers be tacked to the tube to prevent the fibers from moving with respect to the tube during the step of transferring the coupler preform to the coupler draw apparatus. The tacking glue can cause problems in the resultant coupler. Moreover, the off-line method requires additional steps to transfer the tube to the draw apparatus. The previously employed methods of inserting fibers into the tube either on-line or off-line have been tedious, time consuming processes that are sensitive to the manipulations of each operator. This can affect process reproducibility and thus the optical characteristics of the couplers.
Optical fibers must be prepared prior to inserting them into the tube. The protective coating is removed from the portion of the fiber that is to be positioned within the tube during the coupler drawing operation. If the bare portion of the optical fiber is at the end of the fiber, it is preferred that it be provided with a low reflectance termination. An off-line process for forming such a termination is disclosed in U.S. Pat. Nos. 4,979,972 and 5,011,251. Also, the bare fiber portions must be free from contamination. Manual performance of these fiber preparation steps is time consuming and is subject to the particular manipulations of the operator.
During the stripping of coating from the fibers, the termination of fibers, and the insertion of the stripped portions of fibers in the overclad tube, the fibers must be precisely positioned.
In the manual technique for making overclad fiber optic couplers, the fibers were threaded through the glass tube, the tube was clamped into the draw apparatus. Thereafter, the fiber pigtails extending from the glass tube were inserted through vacuum attachments which were then affixed to the ends of the tubes. Such vacuum attachments are unsuitable for an automated apparatus for manufacturing fiber optic couplers. A preferred heat source for forming overclad fiber optic couplers has been a ring burner that directs flames inwardly toward the glass tube. Heretofore, the glass tube has been manually inserted through the ring burner, and its ends were then clamped. Such a burner is not suitable for use in a fully automated apparatus.
In an automated fiber optic coupler manufacturing process, couplers can be made at a greater rate than they could be made by the aforementioned manual process. The heat source must be activated during the stretching of each coupler. This tends to cause the temperature of certain parts of the apparatus near the heat source to become hotter than they did in the manual process. Some of those apparatus parts and the coupler epoxy can be damaged by the higher temperature or can be dimensionally altered whereby process reproducibility is affected. Precautions must be taken to avoid such heat induced damage.
After the coupler has been formed by stretching the overclad tube and fibers, a glue such as an ultraviolet (UV) curable epoxy is inserted into the uncollapsed ends of the tube bore to provide the fibers with pull strength. Conventional off-line epoxy applying and curing techniques are not suitable for use in a fully automated coupler making process since they do not result in the application of a sufficient amount of epoxy into both ends of the bore, and since they are time consuming processes.
In view of the above mentioned disadvantages of conventional methods of manufacturing fiber optic couplers, it is an object of the present invention to provide an apparatus and method of precisely and automatically manufacturing a fiber optic coupler having predetermined coupling characteristics. Another object is to provide a coupler manufacturing apparatus and method in which opportunities for operator caused process inconsistencies are minimized or eliminated.
The present invention relates to various apparatus components and method steps for making fiber optic couplers. Utilization of the invention in its entirety results in the completely automated production of a fiber optic coupler. However, portions of the inventive method and apparatus can be used to improve conventional methods of the type described above. Whereas the present invention is described in conjunction with the manufacture of overclad fiber optic couplers, certain of the apparatus components can be employed in the manufacture of fused biconic tapered couplers of the type wherein two or more fibers are fused together and elongated, without the use of an outer protective glass tube.
The present invention relates to an apparatus for the automated manufacture of fiber optic couplers. Fiber insertion means including adjacently disposed fiber guide tubes insert optical fibers into a glass tube. The fiber guide tubes have fiber input and fiber output ends, the output ends being movable longitudinally with respect to the bore of the glass tube. Means is provided for delivering the optical fibers to the input ends of the fiber guide tubes, with the first ends of the fibers passing through the fiber guide tubes and being deliverable from and retractable into the second ends of the guide tubes. Means is provided for sequentially tensioning each of the optical fibers and for stripping protective coating from the tensioned length of each of the fibers. The apparatus includes coupler draw means that is provided with upper and lower chucks for securing the glass tube at its end regions. The chucks are movable in opposite directions. First and second vacuum seal means evacuate the bore and maintain closed the ends of the glass tube after the stripped regions of the fibers have been inserted into the bore. Heating means heats the glass tube. Programmable control means control the operation of the apparatus.
The coupler draw means can include an upper clamping bar that engages an upper V-groove provided in the upper chuck and a lower clamping bar that engages a lower V-groove provided in the lower chuck; the clamping bars apply a repeatable level of force to the glass tube to secure it in the V-grooves.
The apparatus can include transfer means for transfering a glass tube from a storage magazine to the chucks. This apparatus can include a holding member provided with a groove, delivery means for delivering a tube from the magazine to the groove, and clamping means for gripping a tube. Means can be included for accurately locating the glass tube in the groove. When it is in a first position, the clamping means engages the glass tube held in the groove. The clamping means then moves to a second position and places the glass tube in the chucks of the coupler draw means.
The means for delivering the optical fibers to the fiber insertion means can include at least two optical fiber supplies, and a fiber feed mechanism for paying out a predetermined length of each of the optical fibers from the sources to the fiber insertion means. The programmable control means controls the fiber delivering means, whereby it measures the optical fibers to the predetermined lengths. That is, precise amounts of fiber are advanced from or retracted into the fiber delivering means.
The fiber feed mechanism can include input guide tubes for receiving the optical fibers from the reels, and output guide tubes that are connected to the fiber guide tubes of the fiber insertion means. A fiber extending between the input and output guide tubes is disposed between an idler roller and a motor driven roller. When the idler roller engages the motor driven roller, the fiber is delivered to or retracted from the output guide tube. Fittings are connected to the output guide tubes for introducing a gas therein for reducing friction between the fiber guide tubes and the optical fibers.
A lubricant dispensing tube can be disposed adjacent the fiber feed tubes and extend a distance beyond the ends of the feed tubes to lubricate the bore of the glass tube as the optical fibers are inserted therethrough.
The means for sequentially tensioning each of the optical fibers can include an upper and a lower stripping clamp between which a length of each of the optical fibers is sequentially clamped and tensioned, and the means for stripping the protective coating from the optical fibers can include a stripping nozzle movable transversely and rotatably with respect to the length of optical fiber that is tensioned between the stripping clamps. The stripping nozzle emits a jet of hot inert gas to strip the protective coating away from the length of fiber as the nozzle moves along the coated fiber.
The apparatus can include means for providing a low reflectance termination on an optical fiber. A ball termination torch is vertically and horizontally movable with respect to the optical fibers tensioned between the stripping clamps. After the torch severs the fiber, the stripping clamps retracting in opposite directions.
Bottom clamp means can be provided for clamping one or more of the optical fibers that extend from that end of the glass tube remote from the fiber insertion means.
The heating means is preferably located away from the chucks. After the stripped portions of the fibers are positioned in the tube bore, the heating means moves to a position adjacent the chucks. The heating means can be formed of two sections that close and surround the glass tube.
The upper and lower chucks partially shield the glass tube from the heating means, and in addition, the chucks are maintained at a controlled temperature by water-cooling to enhance process reproducibility.
After the midregion of the glass tube has been heated, the chucks are moved in opposite directions to stretch the tube. The means for delivering fibers and the upper chucks are preferably mounted on a first movable stage, and the lower chucks and the bottom clamp are preferably mounted on a second movable stage, whereby the means for delivering fibers and the bottom clamp move in opposite directions as the tube is stretched.
The apparatus can include dispensing means for dispensing glue into the bore of the glass tube, after a coupler has been formed and means for curing the glue after the glue has been dispensed into the bore. The means for curing the glue can comprise a UV light source sequentially positioned at each of the ends of the glass tube.
A further embodiment includes first and second fiber insertion means, each capable of inserting at least two optical fibers into a glass tube. The first and second fiber insertion means are each provided with at least two adjacent fiber guide tubes that are movable longitudinally with respect to the tube bore. Means are provided for moving the first and second fiber insertion means laterally with respect to the bore. This apparatus is especially useful when used in conjunction with first and second means for forming stripped regions in each of the optical fibers. The first fiber insertion means can be disposed adjacent the glass tube when the second fiber insertion means is disposed adjacent the second means for forming stripped regions.
Yet another embodiment pertains to an apparatus for modifying an optical fiber. It includes means for delivering an optical fiber to a fiber guide tube such that the fiber can move out of and into the fiber guide tube. Means is provided for moving the fiber guide tube from one to another of a plurality of work stations. This apparatus can include means for moving the fiber guide tube toward and away from the first work station.
The invention also pertains to a method of automatically manufacturing a fiber optic coupler. A glass tube is placed into a coupler draw means where its end regions are gripped by upper and lower chucks. At least two optical fibers are delivered to a fiber insertion means. While a length of each of the optical fibers is tensioned between upper and lower stripping clamps, protective coating is stripped from each of the optical fibers, and the fibers are then inserted through the glass tube such that the stripped regions extend within the bore. The ends of the glass tube are evacuated, and the tube is heated. The end regions of the glass tube are drawn in opposite directions to form a tapered coupling region. The steps of the method are controlled by programmable control means.
The glass tube can be gripped in the coupler draw means by securing one of the tube end regions between an upper chuck V-groove and upper clamping bar, and securing the other end region between a lower chuck V-groove and a lower clamping bar, the upper and lower clamping bars applying a force to the glass tube to secure the glass tube in the upper and lower V-grooves. The upper and lower chucks can be maintained at a controlled temperature to improve process reproducibility.
The glass tube can be placed into the coupler draw means by automatically transferring the glass tube from a glass tube storage magazine to the draw means.
The optical fibers can be delivered to the fiber insertion means by paying out each of the optical fibers from fiber sources to fiber guide tubes of the fiber insertion means. The fiber guide tubes can move longitudinally with respect to the bore of the glass tube. A gas can be introduced into the fiber guide tubes to reduce friction between the fibers and the tubes and to remove debris from the fibers entering the guide tubes.
A stripped region can be formed on a fiber by positioning the fiber guide tubes above a lower stripping clamp, and delivering a length of an optical fiber is delivered through one of the fiber guide tubes to the lower stripping clamp which grips the fiber at a first location. The guide tubes are moved upwardly so that the upper stripping clamp can grip the fiber at a second location. The fiber is then tensioned between the first and second locations. A jet of hot inert gas is directed onto a predetermined region of the tensioned fiber to heat it and strip coating therefrom.
A low reflectance termination can be provided on an optical fiber prior to inserting it through the glass tube. The fiber is tensioned between two spaced points. A ball termination torch is moved from a given location in a given direction with respect to the optical fiber such that a portion of the flame severs the fiber into two pieces each having a tapered end. At least one of the tapered ends is retracted away from the other of the tapered ends. The torch continues to move such that the flame heats the retracted tapered end to cause it to become shortened and rounded.
A lubricant is preferably dispensed into the glass tube when the optical fibers are inserted therethrough. This can be done by disposing a dispensing tube adjacent the fiber guide tubes, and dispensing the lubricant therefrom.
The method can further include dispensing glue into the uncollapsed ends of the bore of the glass tube after the tapered coupling region has been formed. The glue can initially be cured by directing UV light beams at each of the end regions of the glass tube while the glue is being applied to the ends of the bore, the flow of the glue stopping when it contacts the light beams. The glue can be further cured by sequentially positioning a UV light source at each of the end regions of the glass tube after the glue has been dispensed into the bore.
Overview of Invention
A brief overview of the method and apparatus of the invention will be given by referring to
(1) Tube transfer apparatus 11 including a tube gripper 14 delivers a glass capillary tube 12 from a storage magazine 13 to coupler draw apparatus 63 where its end regions are secured by upper and lower chucks 64 and 65, respectively. The chucked tube is designated 12'.
(2) Fibers 16 and 17 are delivered from reels 18 and 19, respectively, by fiber feed apparatus 23 to fiber insertion fixture 50.
(3) The fibers are sequentially fed from the fiber insertion fixture to a strip/terminate apparatus 56 where the fibers are sequentially secured within clamps 57 and 58 so that a section of coated fiber is tensioned between the two clamps.
(4) Stripping nozzle 59 emits a jet of hot inert gas that traverses a region of coated fiber to strip coating therefrom.
(5) When appropriate, end termination torch 60 severs the bare fiber that extends between clamps 57 and 58 and forms a low reflectance termination on one or both of the bare severed fiber ends.
(6) The fibers are inserted into the tube 12' so that the bare portions of the fibers extend within the bore of the tube. Valve 43 is actuated to dispense drops of alcohol from source 42 through dispensing tube 44 to the upper end of tube 12' to lubricate the bore as the fibers pass therethrough. Bottom clamps 69 are employed to pull and hold taut one or more of the fibers extending from the bottom end of tube 12' while they are being fed to the upper end thereof.
(7) The end of one or more fibers that extend through tube 12' are affixed to one or more optical fibers 47 which are connected to one or more light sources in measurement system 46.
(8) Bottom vacuum seals 67 are closed onto the bottom end of tube 12' to withdraw alcohol from the bore.
(9) Top vacuum seals 66 are closed on the top end of tube 12' and the bore of tube 12' is evacuated.
(10) Split burner 68 is ignited and closes around tube 12' to heat its mid-region.
(11) Top and bottom chucks 64 and 65, respectively, are traversed in opposite directions to stretch tube 12' and form a tapered coupling region.
(12) Vacuum seals 66 and 67 are opened.
(13) Light beams from upper and lower epoxy locating UV light sources (
(14) Epoxy dispensing apparatus 72 moves to draw apparatus 63, and epoxy dispensers 73 and 74 are positioned at the top and bottom funnels of tube 12'. Epoxy is dispensed through needles into the funnels. As epoxy flows into the uncollapsed ends of the tube bore, the epoxy locating UV beams cure and prevent penetration of epoxy into the bore beyond a predetermined depth.
(15) The epoxy dispensing apparatus is withdrawn, and UV light apparatus 70 is sequentially positioned adjacent the top and bottom ends of the newly formed coupler to cure the epoxy. The epoxy locating UV beams remain energized.
(16) The coupler body is released from the draw chucks. The fiber pigtails at the top of the coupler are metered to the desired length and are severed, whereby the coupler can be removed from the automated manufacturing apparatus.
Various components of apparatus 10 such as the motors, gas operated cylinders, clamping devices and mass flow controllers for methane and oxygen are controlled by programmable controller 79.
Description of Components
All of the components of manufacturing apparatus 10 are secured either directly or by way of supports, brackets and the like to backplate 200. Not all supports are shown. The orientation of elements with respect to backplate 200 is sometimes given relative to an x-axis, a y-axis or a z-axis. Backplate 200 lies in the x-y plane. Movement of an element in the +z direction means movement away from backplate 200 (out of the sheet of FIGS. 4 and 5).
Mechanism 82 is mounted on stage 101 that can be vertically reciprocated on slide 102 by actuating cylinder 103. Clamping device 93 is mounted on a stage 94 that can be reciprocated back and forth on slide 95 by actuating cylinder 96. Clamps 92 are biased open by a spring and are closed by actuating a double piston (pancake) cylinder located within mechanism 93.
Cylinder 96 is actuated to position clamps 92 around the tube that is located in the pickup position in groove members 86. Mechanism 93 is actuated to cause clamps 92 to engage tube 12, and cylinder 103 is then actuated to cause the V-groove member 86 to be translated downwardly. Cylinder 96 is then actuated to retract the clamps away from the magazine.
Clamp slide 95 is mounted on an arm 107 that is rotatably connected to support bracket 108 by double piston rotary cylinder mechanism 106. When mechanism 106 is actuated, arm 107 rotates about 90E and positions clamp mechanism 93 in alignment with the coupler draw apparatus 63 where the tube in clamps 92 is directly in front of the V-grooves of chucks 64 and 65.
Various modifications could be made to the disclosed dispensing mechanism. The tubes would not need to be gravity fed if means such as a spring were employed to supply them to cylinder 84. Moreover, cylinder 84 could be replaced by a wheel having a plurality of slots. A glass tube from the supply of tubes would enter a slot of the slotted wheel and be rotated until it reached an orientation at which the tube would fall from the slot into grooves 86. Cylinder 84 could also be replaced by a pair of sequentially operated gates that are capable of preventing movent of the first two tubes in the linear supply of tubes. A first gate holding the last tube would retract so that the last tube could roll to grooved member, while the next to last tube is held by a second gate to prevent the remaining tubes from also rolling to the grooved member. The first gate then moves into position while the second gate retracts to permit the supply of tubes to roll to the first gate.
Chucks 64 and 65 are shown in
After cylinder 96 (
Since the tube had been precisely positioned in groove member 86 of the tube transfer apparatus, the ends of the tube are vertically positioned to within about 0.1 mm of the desired location in the coupler draw apparatus so that operations such as epoxy application can be properly performed. Properly positioning the tube also ensures that the coating edge of the stripped fiber will be positioned the proper depth in the tube funnel so that epoxy can be properly introduced into the funnel and bore of the tube.
The chucks are designed to achieve the automated loading of the capillary tube while also enabling a repeatable load level to be applied by bar 113 to the tube since bar 113 is actuated by air cylinder 117. The force applied by bar 113 to the tube can be controlled by regulating the air pressure applied to that cylinder.
The chucks partially shield the vacuum seals from the high temperature flame. When the vacuum seals are closed, the elastomeric seals 288 are shielded from the flame by the chucks. The water cooling of the chucks allows the coupler draw process to have a relatively short cycle time since the chucks would otherwise become so hot after a few couplers had been made that process consistancy could not be maintained. The coolant water, which is pumped from a temperature controlled reservoir, maintains correct temperature regardless of timing differences between runs. Deviation of chuck temperature from a given temperature range affects the optical properties of the resultant coupler.
Apparatus for delivering fibers is shown in
If rotatable fiber reels were employed, measurement pigtails 20 and 21 could be connected to measurement system 46 by rotatable connectors. Moreover, the fibers need not be stored on reels. Rather, they could be merely coiled or be stored in boxes.
The cross-hatched portions of
Cylinders 28, 29 and 121 are affixed to roller mounting plates 123 that are attached to movable stages 125 of ball slides. The fixed stages 124 of those ball slides are attached to aluminum plates within the housing. The piston rods are threaded in nuts that are located within fixed yokes. Cylinder 31 is a pancake cylinder from which extend two posts 127 that thread into the metallic block of the clamp 30 which is provided with a synthetic rubber layer 128. Bar 32 is also provided with a synthetic rubber layer 129.
The ball slides described herein, which were made by Daedal, Inc., Harrison City, Pa, include a stage having a U-shape cross-section and a ball slide positioned within the stage. Ball bearings, which are situtated in spaced openings in (racks) that separate the stage and slide, traverse along (tracks) in both the stage and the ball slide.
To feed optical fiber into fiber feed apparatus 23, the idler rollers and clamps 30 are retracted. The fiber is fed through an input guide tube 132, over the respective idler roller and into output guide tube 133 which is connected to T-fitting 39. Output guide tubes 133 are supported by brackets 131 that are positioned by spacers 130. A sufficient length of fiber is fed into the guide tubes to enable it to extend from the ends of the guide tubes at insertion apparatus 50. Clamps 30 are then closed. The protruding fibers can be cut by a mechanism (not shown) in apparatus 10, or they can be manually severed by bending them sharply at the point where they extend from their respective guide tube. The ends of the guide tubes are sufficiently sharp that the fibers become severed at the ends of those tubes. This is the starting position for the coupler making process.
T-fittings 38 and 39, located near the input ends 40 and 41 of the guide tubes, introduce a gas such as nitrogen, air or the like into those tubes. Gas flowing from the input ends 40 and 41 blows dust and debris from the fibers before they enter the tubes. Gas flowing through the guide tubes to the ends thereof at fiber insertion fixture 50 lowers the friction between the guide tubes and the fibers.
Motor 25 could be a d.c. servo motor or any other motor that can accurately rotate roller 24 and thus accurately position the fibers. Moreover, clamps 30 could be eliminated if a separate motor were employed for each set of rollers.
Fiber insertion apparatus 50 (
Retaining tube 51 and fitting 49 are employed so that tubes 35, 36 and 44 can easily be positioned relative to one another. However, retaining tube 51 and fitting 49 can be eliminated by merely gluing tubes 35, 36 and 44 together into a triangular array as shown in FIG. 13. The assembly of tubes can in turn be affixed to support arm 55.
As shown in
Strip/terminate apparatus 56 is shown in greater detail in
Base plate 160 is mounted on stage 161 which is movable along slide 162 which is secured to vertical support plate 163. Gas operated cylinder 181 is mounted on stage 161. Piston 182 of cylinder 181 is threaded into plate 163.
Mounted on base plate 160 are linear slides 165 and 166 on which mounting brackets 167 and 168 are movably mounted. The extent of movement of the mounting brackets 167 and 168 is restricted by adjustable screw stops 169. Four Clippard gas operated pistons (model No. SM-3) 171-174 are mounted to brackets on base plate 160. Pistons 175 and 176 are adapted to engage tab 179 protruding from stage 167, and pistons 177 and 178 engage tab 180 protruding from stage 168.
Stage 161 is normally retracted against support plate 163. Cylinder 181 is actuated to move stage 161 away from plate 163 to a position along the z-axis where fiber 17 (extending from guide tube 36) extends between clamps 156 (clamps 57 and 58 of FIG. 2). Mechanisms 154 are actuated to cause clamps 57 and 58 to close on the fiber. Gas operated pistons 172 and 173 are actuated, whereby pistons 176 and 177 engage tabs 179 and 180, respectively. This applies forces to the tabs that tend to move stages 167 and 168 in opposite directions, whereby coated fiber 17 is tensioned between clamps 57 and 58.
The apparatus for positioning stripping nozzle 59 is shown in FIG. 19. Stripping nozzle 59 is rotatably connected to support bracket 190 by double piston rotary cylinder mechanism 191. Support member 190 is affixed to the rotatable stage 193 of rotating mechanism 194 that is controlled by motor 195. Mechanism 194 is supported by an arm 196 that is affixed to stage 197 that is movable vertically along track 198 when motor 199 is energized.
When mechanism 191 is actuated by pistons 192, stripping nozzle 59 rotates to the horizontal position. Actuation of rotary mechanism 194 and motor 199 lowers stripping nozzle 59 and rotates it to a position directly in front of coated fiber 17.
Coating material 212 was to be removed from coated fiber 210 between points a and b along a section thereof that was held between clamps 57 and 58. Stripping nozzle 59 was rotated from its resting position to a horizontal orientation. It then traversed downwardly and rotated toward the coated fiber. Referring to
The low reflectance end termination apparatus of
The operation of the fiber severing and end termination torch 60 is illustrated in
If clamps 57 and 58 move the same distance (about 1-2 mm has been found to be suitable), a low reflectance ball termination will form on both of the tapered regions. If only top tapered region 265, for esample, is to be provided with a ball termination, clamp 58 can be moved a greater distance (perhaps a few centimeters) while clamp 57 moves about 1-2 mm, whereby only tapered region 265 is provided with a low reflectance termination, and tapered region 266 is moved out of the influence of the flame.
The upper left vacuum seal 66 is shown in
The upper right vacuum seal 66 (
Associated with each vacuum seal is an air cylinder 293, the piston rod 294 of which is affixed to a bracket 295 extending from bracket 286. Cylinders 293 can be actuated to open or close the vacuum seals.
Burner 68 is shown in
Burner close mechanism 314 is affixed to a bracket 321 which is affixed to stage 322. Stage 322 moves in the direction of the double headed arrow along slide 323 which is affixed to support 324. Support 324 includes a rib 325 having an opening in which cylinder 327 is fixedly mounted. The end of cylinder rod 328 is connected to a yoke at the end of bracket 321. Support 324 is secured to back plate 200.
It is convenient to ignite the flame when the burner is in its retracted position shown in FIG. 30. During ignition (and during movement of the burner to tube 12') methane flows at the level that would be required to heat tube 12', but oxygen flows at a reduced level to reduce the amount of heat produced. When the gas and oxygen are turned on, these gases flow up the lower portion of flame shield 330 to silicon carbide resistance ignitor 329. When the gases ignite, the flame propagates in the +z direction through the channel formed by the flame shield to protect those components located above the burner. After the burner halves close around tube 12', the oxygen flow is increased to provide a sufficiently hot flame to soften the tube so that it can collapse and be stretched.
Epoxy application apparatus 72 is shown in
Stages 345 and 346 are mounted on a support member 350 which is mounted on a rotary stage 352 which rotates with respect to base 353 when motor 354 is energized. Base 353 is affixed to stage 355 which is translatable along track 356 in the x-direction when motor 357 is energized. Track 356 is mounted to back plate 200 by mounting bracket 359.
Apparatus for positioning the UV light source is shown in FIG. 35. Light is supplied to UV light sources 370 and 371 by light guide cables 372 and 373, respectively. Sources 370 and 371 are affixed to a post 374 that is connected to the top end of L-shaped support arm 377. The opposite end of arm 377 is affixed to rotary stage 379 which rotates upon base 380 when motor 378 is activated. Rotary stage base 380 is mounted to a linear stage 381 which moves vertically along track 382 when motor 383 is activated. The resting position of arm 377 is shown in FIG. 35.
The operation of bottom clamps 69 can be understood by referring to FIG. 5. Clamps 69, which are Sommer ultramatic cam-action grippers Model No. GP-19, are operated by a mechanism 390 which is mounted on an L-shaped support arm 391. The support arm is affixed to a linear stage 392 which moves vertically along track 393 when motor 394 is energized. Track 393 is mounted on bottom draw stage 300.
Making a Coupler
Various 1×2 couplers including the 3 dB achromatic coupler disclosed in U.S. Pat. No. 5,011,251 (which is incorporated herein by reference) were made by the process that is generally described below. The flame temperature, length of pull, and characteristics of the capillary tube and optical fibers depend on the specific type of coupler being made. To make the coupler disclosed in U.S. Pat. No. 5,011,251 the two optical fibers had different chlorine concentrations in their claddings. The outside diameters of the optical fiber and the protective coating were 125 μm and 250 μm, respectively. Doped silica capillary tubes having a length of 34 mm, an inside diameter of 270 μm and an outside diameter of 2.8 mm were utilized. Funnels at the ends of the tubes communicated with the bore.
Referring to
To deliver fiber 17 to guide tube 36, cyclinder 29 was actuated, thereby engaging roller 27 onto roller 24. Motor 25 turned roller 24 in the clockwise direction of arrow 24a (FIG. 2). When a sufficient amount of fiber had been delivered, idler roller 27 retracted from main roller 24, and cyclinder 31 was actuated to lower clamp 30 against bar 32 to prevent further movement of the fiber. During the time that fiber 17 was being delivered, a position holding clamp (not shown) clamped fiber 16 against bar 32 to prevent it's movement. During the delivery of fiber 17 to guide tube 36, cylinder 31 was actuated to retract clamp 30 from bar 32.
Motor 53 (
Stripping nozzle 59 was rotated to a horizontal position and was lowered to a y position at which stripping was to start to occur. It was then rotated about rotary mechanism 194 to position the end of nozzle 225 (
Ball termination torch 60 was lowered from its resting position position to that level at which fiber 17 was to be severed; it then moved in the -z direction at 38.1 cm/minute. After it moved past the fiber, torch 60 reversed direction and traversed the fiber at 3.81 cm/minute, whereby the fiber became severed. Top clamp 57 moved upwardly about 1-2 mm, and bottom clamp 58 moved downwardly a few centimeters so that tapered end 266 was out of the influence of the flame. As torch 60 continued to move in the +z direction, a rounded, low reflectance termination was formed on tapered region 211a as described in conjunction with
Sometimes optical fiber has a characteristic referred to as "fiber curl" caused by unequal stresses on different sides of the fiber. This could cause the end of fiber 17 which extends from clamp 57 to bend so that it is out of the influence of flame 260 after the fiber has been severed. This can be prevented by keeping the length of fiber extending downwardly from clamp 57 relatively short. To accomplish this, the distance between clamps 57 and 58 should be relatively short, about 4 cm or less being suitable.
Retaining tube 51 was moved to a position such that guide tubes 35 and 36 and dispensing tube 44 were located just above upper strip clamp 57. Stripping nozzle 59 was rotated to horizontal position, lowered and rotated to a position where the hot jet was directed below dispensing tube 44. While the stripping nozzle remained stationary, fiber 16 was fed from the guide tube 35 through the heated gas stream. After coating material was stripped from about 2.5-7.6 cm of the fiber, stripping nozzle 59 rotated away from the fiber, and all but about 1.3 cm of fiber 16 was retracted into guide tube 35. Retaining tube 51 moved downwardly until the end of fiber 16 enterd the capillary tube bore. Fiber 16 was fed through tube 12' until a length appropriate for forming a connection pigtail (about 2 meters, for example) extended from the bottom of the tube. Drops of ethyl alcohol were delivered from dispensing tube 44 while fiber was being fed through tube 12'. The end of fiber 16 that had been end stripped was cleaved, and the cleaved end was put into a cam operated fiber splice assembly tool to temporarily connect it to light source fiber 47 of measurement system 46.
Retaining tube 51 was retracted from tube 12', and fiber 16 was delivered at the same speed so there was no relative movement between fiber and tube. When guide tube 35 was above strip clamp 57, strip clamp 58 closed; strip clamp 57 then closed. The air cylinders 172 and 173 were actuated to tension the fiber between the strip clamps 57 and 58 for the coating strip operation.
A section of coating was stripped from fiber 16 in the same manner as previously discussed in connection with fiber 17. The resultant bare region was slightly shorter than the length of tube 12' (about 30 mm). Strip clamps 57 and 58 then released the fiber.
Through fiber 16 was retracted until the stripped region remained about 0.6 cm from the end of the guide tube 35. The retaining tube and guide tubes were not moving downward toward tube 12' at this time.
Bottom clamp 69 closed on that portion of fiber 16 extending from the bottom of tube 12'. Motors 53 and 394 were energized, and retaining tube 51 and bottom clamp 69 moved downwardly at the same rate. Drops of alcohol were fed from dispensing tube 44 as the stripped regions of fibers 15 and 16 were simultaneously lowered toward tube 12'. As retaining tube 51 was moved toward tube 12', the stripped end of fiber 17 was fed from guide tube 36 until the end of fiber 17 was positioned at about the center of the stripped region of fiber 16. At this time fiber 17 was no longer fed from guide tube 36, and both fibers were advanced downwardly by movement of retaining tube 51 and lower clamp 69 until the stripped midregion of fiber 16 was centered in the bore of tube 12'. At this time the tip of fiber 17 was located at about the longitudinal center of tube 12'. Fiber 17 was then fed from guide tube 36 until the bare region thereof extended adjacent the stripped midregion of fiber 16 through tube midregion 399 as shown in FIG. 36.
If the bare region of fiber 17 were positioned adjacent the bare region of fiber 16 above tube 12', and both fibers advanced together into the bore of tube 12', the surface tension of the alcohol could cause the bare region of fiber 17 to twist about the bare region of fiber 16. This could affect process reproducibility. The solution to the problem is to deliver the fibers as described above such that the bare region of fiber 16 is positioned in the tube bore first, the tip of fiber 17 being midway down the tube bore and thereafter advancing the bare portion of fiber 17 the remainder of the distance into the bore until both fibers are positioned as shown in FIG. 36.
Bottom vacuum seal 67 was closed, and alcohol was evacuated from the bore of tube 12'. During this step, which lasted about 20-60 seconds (20 seconds being typical), air was pulled through the bore of tube 12'. Air was also bled into left vacuum seal 67 through valve 77.
During the vacuum purge of alcohol from the tube bore, a reference measurement was made by system 46.
Retaining tube 51 was raised and fibers 16 and 17 were fed through tubes 35 and 36 at the same rate until the bottoms of tubes 35, 36 and 44 cleared the top vacuum seals 66.
The top vacuum seals closed, and the bore of tube 12' was evacuated. Air was bled through valve 76 and into one side of the vacuum seal 66 while the other side of vacuum seal 66 was evacauated. This generated a fast moving air stream that removed any alcohol that had accumulated on the top of tube 12'.
The aspirator function, i.e. the bleading of air through valves 76 and 77, occurs at any time that vacuum seals are closed. The aspirator function occurs not only during alcohol removal but also during the evacuation of the tube bore during the later described steps of collapsing the tube onto the fibers and stretching the tube to form a coupler. This is not detrimental to the tube collapse step since only a low level of vacuum is required during that step.
With methane flowing at a rate of 0.5 slpm (full operating level) and oxygen flowing at a rate of 0.1 slpm (a level below operating level), burner sections 310 and 311 were ignited. Cylinder 327 was actuated to move split burner 68 in the -x direction, whereby burner sections 310 and 311 were positioned such that tube 12' was centered within annular regions 316 and 317 (FIGS. 30-32). Burner close mechanism 314 was then actuated to cause sections 310 and 311 to close around tube 12'. At that time the flow of oxygen was increased to full operating level (1 slpm), and the midregion 399 (
Burner 68 opened and retracted in the +x direction away from tube 12'.
The first pull was intentionally performed such that less than the desired coupling was obtained. An optical measurement was made to determine the amount of coupling that resulted from the first pull. This information was input to the programmable controller, and a second pull was performed.
The burner flame was ignited as described above, and the burner again moved in the -x direction and closed about the tube. About 2-10 seconds after the application of the full intensity flame to the tube (typically about 8 seconds), the top and bottom chucks 64 and 65 were again traversed in opposite directions a total of 2.6 mm. As soon as the stages started to pull the coupler, the programmable controller reduced the flow of oxygen to the burner to zero in 0.75 second. The burner opened and retracted in the +x direction. The burner was shut off.
The combination of the tube collapse and stretch steps resulted in the formation of a coupler 400 (
The vacuum seals were opened.
The epoxy was stored in reservoirs 360 and 361 which were attached to support member 350. Pressure controllers 362 and 363 pressurized reservoirs 360 and 361 at 24 psi and 33 psi, respectively. The epoxy was a mixture of the following components: (a) 33.11 weight percent ELC 2500, an epoxy resin/photoinitiater blend made by Electrolite Corp., Danbury, Conn., (b) 0.34 weight percent additional photoinitiator, (c) 58.23 weight percent magnesium pyrophosphate filler (screened to 35 μm), and (d) 8.32 weight percent 1.5 μm silica microspheres made by Geltech Corp., Alachus, Fla. The viscosity of the epoxy at 25EC, 58EC and 82EC is approximately 80 poise, 10-15 poise and 4 poise, respectively.
Rotary stage 352 rotated 90E (in the counter-clockwise direction when observed from the top or +y direction) to position devices 340 and 341 farther away from apparatus backplate 200 so that the epoxy application apparatus would clear other equipment as it traverses toward the draw apparatus 63. Stage 355 then moved in the -x-direction, and rotary stage 352 rotated further in the above-described direction. This positioned epoxy application devices adjacent coupler 400 (
The angular orientation of top needle 338 did not seem to be critical. The size of needle 338 was 22 gauge. With the end of the needle positioned immediately above the top funnel, actuator 340 was energized 1.75 seconds to deliver a drop of epoxy which, assisted by gravity and capillary action, flowed into the top funnel and into the top bore.
When a needle 339 of similar size was employed to apply epoxy to the bottom funnel, an insufficient amount of epoxy traveled into the bore. Reasons for this are as follows. The ends of the tube reach a maximum temperature of about 95EC during the last stretch step. At the time that the epoxy is applied, the temperature of the top and bottom of the tube has decreased to about 82EC and 58EC, respectively. Moreover, the temperature continues to decrease as the epoxy is being applied. This causes the viscosity of the epoxy in the bottom funnel to be higher than that in the top funnel as mentioned above. Also, the epoxy in the bottom funnel must flow upwardly. The following steps were taken to ensure the proper application of epoxy to the bottom funnel and bore. The epoxy applied to the bottom funnel was supplied at a higher pressure, and bottom needle 339 was smaller than needle 338, needle 339 being a size 18 gauge. Needle 339 was oriented at an angle of about 30E from vertical. In general, needle 339 should be oriented less than 45E from vertical. This enables the tip of needle 339 to be positioned deep in the funnel as shown in FIG. 37. In addition, the tip of needle 339 is beveled such that its opening is oriented horizontally or nearly horizontally. This causes the epoxy to be directed up the funnel toward the bore. Since the epoxy is applied to the bottom funnel at higher pressure through a smaller needle, it squirts up into the funnel and reaches the bore where it flows upwardly under the influence of capillary action as well as the force caused by a pressure reduction in the bore due to the cooling of the coupler. The same amount of epoxy is applied to the top and bottom funnels. Because of the small needle size, the flow rate into the bottom funnel was lower; therefore, the actuator 341 was energized 4.2 seconds to deliver a similar drop of epoxy to the bottom funnel.
After a drop of epoxy was injected into each funnel, the needles were retracted vertically from the funnels and were moved away from the longitudinal axis of tube 12'. This caused the epoxy drops to release from the needles. The first application of epoxy was insufficient to completely fill the funnels. If the funnels had been completely filled, an air bubble could have formed and prevented the epoxy from advancing a sufficient distance into the bores. UV light from sources 297 caused the epoxy to cure and cease flowing after it had flowed a predetermined distance into the bores.
After about 3-10 seconds (5 seconds is typical) had elapsed to permit the epoxy to traverse through the funnels and into the tube bores by capillary action, needles 338 and 339 were again positioned at the funnels. A second drop of epoxy was dispensed into each funnel; this drop was sufficient to fill each funnel. The epoxy application apparatus then moved to resting position. The epoxy filled the funnels, which were about 2.5 mm deep and extended into the bores a distance of about 3.5 mm.
In the resting position of arm 377 (
When the coupler is sufficiently cool (30-45 sec) an optical measurement is made.
The coupler body is released from the draw chucks.
The fiber pigtails at the top of the coupler are metered out by the fiber feed apparatus until about 2 m of fiber extends from the top end of the coupler. The output pigtails are then severed by a cutting tool or by bending fibers 16 and 17 to a tight radius at the ends of guide tubes 35 and 36. Coupler 400 is removed from the draw.
The specific example concerns the formation of 1×2 couplers. The above-described manufacturing apparatus could also be employed to make 1×N couplers of different configurations such as the 1×6 and 1×8, for example. To make a 1×6, guide tubes 410 could be arranged in a six-around-one configuration within a retaining tube 411 (FIG. 38). More than one alcohol dispensing tube could be employed. Also, since it may be desirable to maintain the guide tubes in the illustrated close packed array, the alcohol dispensing tubes can be situated outside the retaining tube. Three dispensing tubes 412 are shown as being equally spaced around the retaining tube.
To make a 1×8, guide tubes 420 could be arranged in an eight-around-one configuration within a retaining tube 421, a spacer tube surrounding the central guide tube (FIG. 39). Three dispensing tubes 422 are equally spaced around retaining tube 421.
A semi-automatic coupler manufacturing apparatus could employ some of the components shown in
The duplication of certain functions would decrease the time required to make a coupler.
The fiber feed apparatus and fiber insertion apparatus shown in
The first work station 445 could be one containing a stripping nozzle for stripping coating material from the end of fiber 441. The fiber could be retracted into tube 440, and that tube could be moved to second work station 446 where the stripped end could be inserted into a grinding machine that forms a lens on the end of the fiber. The lensed fiber could be retracted into tube 440 and moved to third work station 447 where a layer of gold could be deposited thereon by sputtering or the like. The resultant fiber would be suitable for use as a laser diode pigtail. The gold layer enables the fiber to be soldered to a fixture with the lensed end in light receiving relationship with the laser diode.
Miller, William James, Morrell, Mark Leon
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